We shall be extending our studies utilizing the nuclear modulation effect in pulsed EPR spectroscopy to examination of low spin cobalt complexes. In a protein such as cobalt substituted myoglobin and in a model compound, we shall try to determine what is the effect of the protein on the magnetic interaction and on the bonding between the metal and its ligands. We shall also use the nuclear modulation effect to determine the metal binding ligand structures of Fe(III), Co(II), Cu(II) and Fe(II)-NO-bleomycin. We shall be studying stopped flow kinetics of the ferrous bleomycin complex with molecular oxygen in order to determine whether an oxygenated complex is formed before DNA breakage. EXAFS studies will be performed in order to test the hypothesis that copper and iron in resting cytochrome a3 are associated with each other as a mu-oxide.